Silver halide emulsion for color photography



Patented Oct. 12, 1943 e UNITED STATES PATEN oFFicE assists I SILVER l IAL'IDE EMULSION FOR 0010!! PHOTOGRAPHY Richard V. Young, Rochester NLY 'assignor to Eastman Kodak Company, 'Rochester N. 1., a corporation of New Jersey N Drawing Application December 23 1940 Seual No. mass. In Great Britain 15mm, 18,

(out-v) This invention relates to color photography and more particularly to non-diflusing resinous dyes tor use in color photography.

In photographic color processes it has been suggested that color images may be produced in sensitive multilayer coatings of dyed gelatin by bleaching out dyes with hydrosulfite or stannous chloride in the area of silver particles resulting from the development of a latent image. Such a process has been described in Christensen U. S.

Patent No. 1,517,049 and other more recent 6 Claims:

ence of these suhstituents. However, the presence of these negative substituents in another portion or the dye molecule is generally without efleet For example, in a dye-containing a 1,8-dihydroxy-' naphthalene--sulionic acid residue the presence of the sulfonic group in the position para to one hydroxyl does not markedly influence the course patents.- It is important in this method of color development that the dyes used for coloring the sensitive gelatin layer be substantially non-ditiusible in order that they do not wander irom the layer and impart undesirable color to adjacent layers. One method oi! accomplishing this is known to the art and consists in precipitating dyes in emulsion layers by means oi appropriate reagents.

One object of the present invention is to provide sensitive emulsion layers with non-diffusing dyestufls. for preparing more non-diiiusible dyestuils for these purposes. A iurther object is to provide an Another object is to provide a method or the reaction of an aldehyde at the ortho'and para positions relative to the/rother hydroxyl.

Dyes which I react with, c i-aldehyde are those readilyreducible withybleaching solutions such as hydrosulflte ormlkaline ous chloride.

The following dyeskare representative of the v well known dyes which may be caused to react with aldehydes or aldehyde forming compounds to give water-soluble resinous non-diflusing dyes according to my invention.

improved photographic element for use in color photography having superposed emulsion layers containing dyestufls fast to diflusion.

These objects are accomplished in the present invention by adding to a sensitive 'silver halide emulsion a non-difluslble resinous dyestufi formed by the reaction of an aldehyde or 'aldehyde-iorming compound with an azo dye having at least one ortho or para position not substimted.

The non-diflusible resinous dyestufls' of this invention are prepared by means of the adaption of the well known reaction of a phenol or aryl amine with an aldehyde. Water-soluble dyes which are normally notiast to difiusion in emulsion layers and are reducible with hydrosulfite or alkaline stannous chloride are reacted with an aldehyde such as iormaldehyde or with aldehydeforming compounds such as hexamethylenetetramine or paraiormaldehyde. The dyes which best lend themselves to this reaction and which are very useful in color photography are the azo dyes characterized by the fact that they contain a phenolic, naphtholic or aryl amine residue, one

" or more ortho or para positions of which are not substituted. Also itis preferable that the dyes contain no negative substituents such as carbonyl, nitro, or sulfonic acid in the reactive phenolic. naphtholic or aryl amine residue, since the c ndensation is markedly slowed down by the p es- EEOQFNOOH I Brilliant, Paper Yellow.

The resinous dyes of my invention may be prepared by reacting iormaldehydewith a dye. the preferred method being-to reflux air-alkaline solution of the dye with an excess of 35-40% formalin solution for several hours and until it is determined by diffusion tests of the product in gelatin layers that the simple dye has been converted to the resinous state. In an alternative method I reflux a diethyleneglycolmonobutyl ether solution of the dye with hexamethylenetetramine in which case the dyecondenses with the aldehyde liberated to form the resinous dye of my invention. In a similar manner I treat a dye with paraformaldehyde.

Where a large number of dye molecules are so combined the product may be represented by the following molecular structure:

where D represents the dye molecule and the dye is condensed with formaldehyde, 1: being a large integer.

Photographic emulsions are prepared in the usual. manner using the resinous dye of this invention. To a solution of a colloidal material such as gelatin are added silver nitrate and a soluble alkali metal halide salt such as potassium bromide, and the resinous dye of the invention.

The amount of resinous dye which is added varies with the color saturation of the particular resinous dye in use. The resulting photographic emulsion which contains a sensitive silver halide salt and the resinous dye is coated upon a support in the usual way. Multi-layer photographic elements are prepared by superposing several emulsion layers containing sensitive silver halide and diflerent non-diflusible resinous dyes. Instead of gelatin the carrier for the emulsions may consist of other colloidal materials such as cellulose esters or natural or synthetic resins.

The photographic emulsions which I describe are processed by the well" known method of catalytically bleaching out the coloring material in the area of the silver particles deposited by negative processing, followed by the removal of the negative silver.

A bleaching solution which is suitable for the catalytic bleaching of emulsions containing the resinous dyes ofthe invention is one having the following composition.

Stannous chloride gm 8 Water 100 Sodium hydroxide (10% solution) cc-.. 100

This bleach bath has been described in more detail and with variations in Seymour U. 8. Patent No. 2,184,022. Another suitable bleach bathis A suitable solution for removing the negative silver from a film is one. having the following composition:

Potassium ierricyanide gm -50 Ammonium hydroxide 28% cc 2% Potassium bromide gm 5 Water to cc 1000 My invention is capable of numerous variations as other dyes besides those mentioned may be caused to form resinous dyestuffs by reaction with an aldehyde. In photographic color processes utilizing the bleaching method of producin dye images I am limited to those dyes which will react with an aldehyde and the condensation products of which are bleachable in a known manner. I may however use these non-diflusible resinous dyes as constituents of light absorbing filter layers in this and other color processes. It is to be understood that my inventionis to be limited only by the scope of the appended claims.

What I claim is new and wish to secure by Letters Patent of the United States is:

1. The method of preparing a light-sensitive photographic emulsion for the bleach-out process .of color photography which comprises uniformly dispersing in a silver halide emulsion a noncoupling non-diflusing water-soluble resinous dye formed by union of a formeldehyde with an azo dye having a group selected from the class consisting of hydroxyl and amino groups, and capable of being bleached in the region of a silver image, a position other than meta, with respect to said groups, being unoccupied prior to said reaction. the coupling of the aldehyde with the azo dye occurring in said unoccupied position.

2. The method of preparing a light-sensitive photographic emulsion for the bleach-out process of color photography which comprise uniformly dispersing in a silver halide emulsion a noncoupling non-diffusing water-soluble resinous dye formed by union of formaldehyde with an azo dye having a group selected from the class consisting of hydroxyl and amino groups, and capsbie of being bleached in the region of a silver image, a position other than meta, with respect to said groups, being unoccupied prior to said reaction, the coupling of the aldehyde with the azo dye occun'ing in said unoccupied position.

3. The method of preparinga light-sensitive photographic emulsion for the bleach-out process of color photography which comprises uniformly dispersing in a silver halide emulsion a noncoupling non-diffusing water-soluble resinous dye formed by union of 8. formaldehyde with an azo dyehaving a hydroxyl group, and capable of being bleached in the region of a silver image, a position other than meta, with respect to said group, being unoccupiedprior to said reaction, the coupling of the aldehyde with the azo dye occurring in said unoccupied position.

4. The method of preparing a light-sensitive photographic emulsion for the bleach-out process of color photography which comprises uniformly dispersing in a silver halide emulsion a noncoupling non-diffusing water-soluble resinous dye formed by union of a formaldehyde with an azo dye having an amino group, and capable of being bleached in the region of a silver image, a posibeing unoccupied prior to said reaction, the coupling of the aldehyde with the azo dye occurring amino groups, and capable of being bleached in the region of a silver image, .a position other than meta, with respect to said groups, being unoction other than meta, with respect to said group cupied prior to said reaction, the coupling of the aldehyde with the azo dye'occurring in said unoccupied position. y 1

6. A light-sensitive photographic emulsion for the bleach-out process of color photography, comprising a siiver halide emulsion containing a uniform dispersion of a non-coupling non-diffusing selected from the class consistingor hydrozryl and 0 groups, and capable oi being bleached in the region 01. a silver image, a position other than meta, with respect to said groups, being unoccupied prior to said reaction, the couplingof the aldehyde with the azo dye occurring in said unoccupied position.

RICHABD V. YOUNG. 

